Glare-reducing lamp



A. s. MAKAS GLARE-REDUCING LAMP Filed June 14, 1963 March 8, 1966FUNCTIONAL AREA I J mv NTOR. F I G. 3 m M aw-MM W ATTORNEYS UnitedStates Patent 3,239,659 GLARE-REDUCING LAMP Albert S. Makas, Medford,Mass., assignor to Polaroid Corporation, Cambridge, Mass., a corporationof Delaware Filed June 14, 1963, Ser. No. 287 ,960 2 Claims. (Cl.2409.5)

This invention relates to illuminating means such as a lamp whichproduces polarized and non-polarized light functioning together toprovide both a high degree of illumination and an essentially glare-freeilluminated area.

Although illuminating devices such as so-called reading or desk lamps,positioned generally somewhat above and in front of the user andemploying polarizing filters for glare-reduction purposes with respectto an illuminated surface, have previously been known and havefunctioned with some measure of effectiveness, their principal defecthas been the excessive loss of light which has accompanied theiroperation, due to the large proportion of light absorbed by the filters.On the other hand, where an adequate light level has been maintained,the polarizing efficiency of the filters has been insufiicient to obtainthe desired glare reduction.

The present invention seeks to overcome the aforesaid deficiencies byproviding an illuminating device such as a lamp having the properties ofboth excellent illumination and freedom from glare. More particularly,the invention proposes to embody these properties in a lamp of a typewhereby light rays are predominantly directed downwardly or forwardlyonto a working surface and are reflected in a direction generally towardthe user.

In accordance with the foregoing considerations, a principal object ofthe invention is to provide a lamp assembly of the character describedpossessing characteristics of high efficiency with respect both to itspolarizing capabilities for reducing glare and to the overallillumination which it furnishes.

Further objects are to provide a lamp of the aforesaid category which isof relatively simple structure, of wide utility, and which has anappearance consistent with acceptable design standards.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the product possessing the features,properties and the relation of components which are exemplified in thefollowing detailed disclosure, and the scope of the application of whichwill be indicated in the claims.

For a fuller understanding of the nature and objects of the inventionreference should be had to the following detailed description taken inconnection with the accompanying drawings wherein:

FIGURE 1 is a perspective view of a lamp of the invention, with partsbroken away;

FIG. 2 is a diagrammatic side view of the lamp illustrating itsoperation; and

FIG. 3 is a front view of the light-emitting portion of the lamp,illustrating the directions of functional light rays.

As shown in FIGURE 1, the lamp comprises illumination-providing means,generally indicated at 12, including light source means 14 in the formof a pair of incandescent bulbs mounted horizontally in a socket 16. Thesocket is attached to the inner surface 18 of an elongated, recessed orconcave light shield or shade 20 which partially surrounds the lightsource. The shield 20 may suitably be formed of a metal, glass, aplastic, or the like and, accordingly, may be either opaque ortranslucent.

The inner surface 18, either of itself or by reason of means coatedthereon or attached thereto, constitutes a 3,239,659 Patented Mar. 8,1966 light reflector which generally follows the contour of the shield20. A sheet-like plane-polarizing filter element 22, of given shape anddimensions and having a polarizing axis or direction 23, is mountedacross a limited longitudinal portion only, e.g., a central portion, ofthe open lower face 24 of the shield 20 so as to permit certain directrays from light source 14 to pass downwardly through it, while otherrays, direct or reflected, avoid the filter and pass downwardly throughthe open areas 24a (FIG. 3) beyond its edges. The open areas at eachside of element 22 adjacent to the ends 20a of the shield also permit anefficient circulation of cooling air around the light source 14.

As illustrated in FIG. 2, unpolarized light from the light source 14vibrates in a plurality of directions, indicated at 34. It includeshorizontal vibrations which, if permitted to contribute to, or exist in,direct radiation from the light source 14 to the surface 36, producing avisible image of the light source reflected from the surface 36, wouldcause glare. The light ray 38, typical of rays emitted directly towardsurface 36 and transmitted by plane polarizing filter 22, by reason ofthe latters polarizing direction 23, and to a certain extent becausepart of the horizontal vibrations are reflected from the upper surfaceof the filter 22 and, therefore, are dissipated harmlessly, includessubstantially only vibrations of the type exemplified by vibration 40,that is, vibrations which are disposed at to the horizontal vibrationsor, otherwise stated, light which is vibrating parallel to the paper ofthe drawing. Accordingly, the light transmitted by polarizing filter 22and reflected from the surface 36 or from any object resting thereonwhich is visible to an observer at 42 is free of glare.

As previously intimated, the absorption of light by an efficientpolarizer of the type employed herein is considerable and may, forexample, be as great as sixty percent of the total incident light.Accordingly, the light level at surface 36 may be undesirably low. Thepresent invention overcomes this possibility, as shown in FIG. 3, byproviding the supplementary use of certain non-polarized light rayswhich contribute to illumination of the functional area but which do notconvey an image of the light source directly to the surface 36 andthence to the eyes of the user. A single light source 14 is shown inFIG. 3, it being understood that the invention is not limited to anyparticular type of light source provided that the relative dimensionsand positioning of the light source and polarizing filter and thestructure of the reflector 18, with respect to a functional area underobservation, are correct. These conditions are obtained by providingthat any light rays directed toward surface 36 which might render animage of the light source visible, in the form of glare, shallpreliminarily pass through the polarizing filter 22 to remove the glarecomponent, and that a maximum of the light rays whose directions do notrender the image of the light source thus visible shall enter thefunctional area of the surface 36 laterally as side or crosslighting,without passing through the polarizing filter so as to retain theirmaximum intensity.

Further referring to FIG. 3, the function of polarized and non-polarizedlight rays, operating together to provide a total illumination of thearea of use which considerably exceeds that which would be possible ifthe polarizing filter 22 were to cover the entire aperture 24 of theshield 20, is illustrated in detail. Where, as shown, the centrallylocated filter 22 occupies only one-half of the opening 24 theimprovement in illumination may be greater than fifty percent. Thefunction of the direct, verticallypolarized light component 38, providedby the polarizing filter 22, has been described with respect to FIG. 2,it being understood that plurality of light rays having such raycomponents exists within the limits of the functional area so as toestablish a basic glare-free illumination thereof. The ray 44, twicereflected from the surface 18 and thence directed into the area of use,is illustrative of the aforesaid crosslighting, namely, of the pluralityof contributory reflected rays which bypass the polarizing filter 22 andwhich, by reason of their generally transverse directions, provideadditional illumination of the area without causing visible glare. Theray 46 is representative of direct rays which possess undesirablehorizontal vibrations but which are traveling in directions away fromthe functional area, as scattered light, and are not productive ofglare. Similarly, the reflected ray 4% is typical of those reflectedrays which bypass the polarizing element 22 but which are directedoutside of the area of use and for this reason cause no harmful glareeffects.

EXAMPLE A lamp of the type contemplated herein included, by way ofexample, the following pertinent structural elements and data relatingthereto.

(a) Two 40-watt tungsten lamps 14 were mounted along an axis extendingfrom one end 20a of the shield 20 to the other. Each lamp was positionedwith its filament approximately 2 inches from the rear surface and 4 /2inches from each end of the reflecting surface of the shield. The lampswere located about 10 inches above the surface 36.

(b) The polarizing filter 22 was of an HN35 type, having a transmissionof 35%, and was manufactured by P- laroid Corporation, Cambridge,Massachusetts, U.S.A. The filter was mounted at the center of the shieldaperture 24 so as to extend, transversely of the shield, fromfrontto-rear of the aperture and to terminate, longitudinally of theshield, short of the shield ends 20a. It thus covered about 50% of theentire aperture.

(c) The reflector was an aluminized coating on a surface of asphericalcontour formed on the inner surface of the metallic shield 20. Itincluded portions adjacent to the shield ends 20a which were so curvedas to reflect a large proportion of rays from the light sources 14,laterally, into the functional area to enhance the illumination thereof.Significant reflecting portions adjacent to the shield ends had a radiusof curvature of 6 inches or more.

It will be apparent that various other modifications of the lamp withinthe scope of the invention are possible. The principles involved,obviously, are not limited to a desk lamp and may even be applied to thelighting of vertical wall areas or pictures hung thereon. Although thepolarizing filter 22 is preferred as a separate element, it could be ofa type emboided in or on the envelope of the light source 14, itself,assuming its dimensions to be such as to insure that direct rays arepassed therethrough and indirect rays are passed to the sides thereof.Polarizing means of a type adapted to be formed directly on theenclosure or envelope of a light source is disclosed in US. Patent No.2,252,324, issued to Edwin H. Land. Where a filter 22 of the type shownis employed, its edges should overlie a direct line from the filament ofthe light source to surface 36. The filter 22 may, of course, beotherwise mounted and its shape and size may be altered somewhat fromthose of the rectangle shown, e.g., so that its edges, adjacent to theshield ends 20a are irregular or curved. It is not entirely essentialthat the polarizing element 22 extend to the rear of the shieldaperture, provided that it intercepts direct rays to the surface 36. Thereflector can, of course, be differently shaped and can even includeplanar surface portions. It would also be possible to include atransparent or light-diffusing material in the areas 24a and to provideperforations for heat dissipation elsewhere in the shield. One suchstructure contemplates a sheet of such material completely covering theaperture 24, with the polarizing means 22 mounted thereon.

Since certain changes may be made in the above product without departingfrom the scope of the invention herein involved, it is intended that allmatter contained in the above description or shown in the accompanyingdrawing shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. A lamp for producing both polarized and non-polarized lightfunctioning together to provide a substantially glare-free overallillumination of a remotely located functional surface, said lampcomprising light source means, a recessed, elongated concave lightshield partially surrounding said light source means and having an openface at a side directed toward said surface to be illuminated,reflecting means afiixed to the inner surface of said light shield, asubstantially flat sheet comprising plane light polarizing materialmounted on said shield, said light polarizing material extending acrossa central portion only of said open face for polarizing light rayspassing directly therethrough and being spaced from both ends of saidshield, the reflecting light shield being of such shape and contour thatlight rays from said source and twice reflected from the reflectingsurface are directed into the area of use on said functional surface toprovide additional illumination of said surface without glare, the lightsource being so positioned with respect to the light polarizing materialand reflecting surface that light rays passing directly through the openspaces adjacent to the ends of the light shield and the ends of thelight polarizing material are emitted laterally outside of the area ofuse of said functional surface.

2. A lamp, as defined as claim 1, wherein the axis of said polarizingmaterial is substantially normal to the plane of said functionalsurface.

References Cited by the Examiner UNITED STATES PATENTS 1,773,915 10/1929Short 2409.5 X 2,252,324 8/1941 Land 313-111 2,302,556 11/1942 Kriebel.2,302,613 11/1942 Land 240- 2,402,176 6/ 1946 Marks 240-9.5 X 2,411,18911/1946 Brown 240-81 FOREIGN PATENTS 1,098,406 3/1955 France.

NORTON ANSHER, Primary Examiner.

1. A LAMP FOR PRODUCING BOTH POLARIZED AND NON-POLARIZED LIGHTFUNCTIONING TOGETHER TO PROVIDE A SUBSTANTIALLY GLARE-FREE OVERALLILLUMINATION OF A REMOTELY LOCATED FUNCTIONAL SURFACE, SAID LAMPCOMPRISING LIGHT SOURCE MEANS, A RECESSED, ELONGATED CONCAVE LIGHTSHIELD PARTIALLY SURROUNDING SAID LIGHT SOURCE MEANS AND HAVING AN OPENFACE AT A SIDE DIRECTED TOWARD SAID SURFACE TO BE ILLUMINATED,REFLECTING MEANS AFFIXED TO THE INNER SURFACE OF SAID LIGHT SHIELD, ASUBSTANTIALLY FLAT SHEET COMPRISING PLANE LIGHT POLARIZING MATERIALMOUNTED ON SAID SHIELD, SAID LIGHT POLARIZING MATERIAL EXTENDING ACROSSA CENTRAL PORTION ONLY OF SAID OPEN FACE FOR POLARIZING LIGHT RAYSPASSING DIRECTLY THERETHROUGH AND BEING SPACED FROM BOTH ENDS OF SAIDSHIELD, THE REFLECTING LIGHT SHIELD BEING OF SUCH SHAPE AND CONTOUR THATLIGHT RAYS FROM SAID SOURCE AND TWICE REFLECTED FROM THE REFLECTINGSURFACE ARE DIRECTED INTO THE AREA OF USE ON SAID FUNCTIONAL SURFACE TOPROVIDE ADDITIONAL ILLUMINATION OF SAID SURFACE WITHOUT GLARE, THE LIGHTSOURCE BEING SO POSITIONED WITH RESPECT TO THE LIGHT POLARIZING MATERIALAND REFLECTING SURFACE THAT LIGHT RAYS PASSING DIRECTLY THROUGH THE OPENSPACES ADJACENT TO THE ENDS OF THE LIGHT SHIELD AND THE ENDS OF THELIGHT POLARIZING MATERIAL ARE EMITTED LATERALLY OUTSIDE OF THE AREA OFUSE OF SAID FUNCTIONAL SURFACE.